Definition
A self-checking function built into a GPS receiver that verifies the integrity of the position information it is calculating. It does this by comparing signals from the visible GPS satellites and detecting whether any one of them is producing inconsistent data. If the receiver cannot confirm that the position is reliable, it warns the pilot that the GPS information should not be trusted for navigation.
Plain English
It is the GPS unit's way of checking its own work. If the satellites do not agree with each other, the receiver flags it and tells the pilot the position may be wrong.
Context Anchor
Seen in GPS navigation, instrument flying, preflight receiver checks, and messages that tell a pilot whether GPS guidance is available for a planned operation.
Derivation
Receiver — the GPS unit in the aircraft. Autonomous — does it on its own, without help from an outside source. Integrity Monitoring — checking whether the data can be trusted. Put together: the receiver checks the trustworthiness of its own GPS signals by itself.
Why Pilots Care
Confirms GPS position accuracy so pilots can safely rely on it for navigation and approaches.
Analogy
It is like a scale that weighs the same object several ways and warns you if one reading does not agree with the others.
Intuition Check
Autonomous does not mean the aircraft is flying itself. Here, it means the receiver performs the trust check by itself, using the satellite signals it is receiving.
Example Sentence 1
Before starting the GPS approach, the pilot confirmed that the receiver's integrity monitoring function was available.
Example Sentence 2
Receiver Autonomous Integrity Monitoring alerted the crew to a satellite fault and excluded the bad signal from the position solution.